It is well known that an extremely bright light, rich in ultraviolet and infrared rays, is produced by welding, either in gas welding as well as in electric-arc welding. Prolonged exposure to such light rays may be very harmful to the welder's eyes. It is therefore common practice that welders use a helmet with a protective filter arranged before his eyes or a protective shield comprising a protective filter and manually held in place between the welder's eyes and the welding arc or flame.
A basic problem with such protective means is that the visible light is also greatly attenuated, making it difficult for the welder to see the field of work at the beginning of the welding procedure or after having finished it.